Game playing is practiced in which, with a head mounted display that is connected to a game machine worn on the head of a user, the user operates a controller, for example, while looking at a screen displayed on the head mounted display. With an ordinary stationary display connected to a game machine, the user's visual field range extends also to the outside of a display screen, so that the user may not concentrate on the screen or lose the sense of absorption in the game being played. On the contrary, wearing a head mounted display makes the user look at only the video shown on the display, thereby providing effects of the increased sense or absorption and enhanced game entertainment.